Background Art
Most aircraft employ a fuselage having a constant-section (i.e., center) portion and doubly curved forward and aft sections. While such structures could potentially be produced using a variety of processes, large parts such as stiffened aircraft fuselage skins presently can be made from large axially stiffened near-net extrusions or, alternatively, directly machined out of plate. The use of extrusions are favored from a cost-effectiveness standpoint because extruding involves less labor and utilizes a much greater fraction of the raw material used for producing the fuselage skins. Patents involving the formation of aircraft fuselage skins or other curving structures are U.S. Pat. Nos. 2,230,393; 2,427,065; 2,458,686; 3,096,958; 3,920,206; 3,940,891; 4,310,132; 4,471,609 and 5,154,373, the disclosures of which are hereby incorporated by reference.
For the constant-section portion of the fuselage, the application of extrusions if fairly straightforward because the fuselage skins can be formed with integrally formed stiffeners which are parallel to one another. Wing planks often employ parallel stiffeners in both integral and multi-piece construction because they are substantially flat or singly curved. However, the application of extrusions in the doubly curved forward and aft sections of the fuselage is complicated by the fact that the spacing of the stiffeners typically varies as the fuselage diameter increases or decreases. As will be appreciated, with present day extrusion processes it is not possible to achieve variable spacing of the stiffeners when extruding large stiffened fuselage panels. Thus, doubly curved portions of the fuselage, following present day design and fabrication concepts, can only be made with integrally formed stiffening portions by machining out of non-near-net stock, such as plate, with the associated inefficient material usage.
It would therefore be highly desirable to provide an aircraft fuselage and a method for manufacturing same which allows a plurality of extruded fuselage panels, each having a plurality of integrally formed stiffening elements, to be secured to one another by a plurality of independent members such that doubly curved sections of the fuselage can be formed in a cost effective manner.
It would also be highly desirable to provide a method of forming a complexly shaped aircraft fuselage through conventional extrusion techniques, wherein independent skin panels of the fuselage each have integrally formed stiffening members, and where the integrally formed stiffening members of adjacent skin panels can be secured together by independent fastening members to provide added structural strength and rigidity to the fuselage.
Still further, it would be very advantageous to be able to form an aircraft fuselage having one or more doubly curved portions in which a plurality of fuselage panels are extruded, and where each of the fuselage panels include integrally formed stiffening portions which could be coupled together via a plurality of splice longerons and also via independent fastening members to fasten the stiffening portions of each of the fuselage panels to the splice longerons at the areas where the stiffening portions run out into contact with the splice longerons.